Etiological Factors in COPD Exacerbations

Introduction

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory airway condition associated with episodes of acute deterioration termed exacerbations. Exacerbations are defined by a worsening of symptoms from the usual stable state, especially the symptoms of dyspnea, increased sputum volume, and purulence. Exacerbations are among the most common causes of medical admission in the UK. They are also important events in the natural history of COPD and have been shown to drive lung function decline. Exacerbations are responsible for much of the morbidity and mortality associated with this highly prevalent condition. Exacerbations are associated with increased systemic and airway inflammation, may be triggered by bacterial and respiratory viral infections, and can also be precipitated by environmental factors.

Abstract

Exacerbations of chronic obstructive pulmonary disease (COPD) are associated with increased systemic and airway inflammation and are a major cause of morbidity, mortality, and hospital admission. Exacerbations may be triggered by environmental factors but the majority are infectious in etiology. Bacteria are detected in around 50% of exacerbations and increases in bacterial load and species strain changes are potential key causative mechanisms in acute exacerbations of COPD. Polymerase chain reaction techniques have established that, in half to two-thirds of exacerbations, viruses may be causative pathogens with rhinovirus the most frequently detected respiratory virus at exacerbation. COPD patients may be more susceptible to respiratory virus infections and further work is required to explore the interactions between viral and bacterial infections at exacerbation. Future studies may target the frequent exacerbator phenotype and those patients colonized with potentially pathogenic microorganisms for long-term antibiotic therapy. Respiratory viral infections are also an important therapeutic target for COPD as prevention of viral infection may reduce exacerbation frequency and, hence, improve health status.

Keywords

respiratory viruses, chronic obstructive pulmonary disease, exacerbation, bacteria